Harmonize GridLayout2 and GridData2 with SWT classes

Similar to https://github.com/eclipse-windowbuilder/windowbuilder/issues/963, the [GridLayout2](https://github.com/eclipse-windowbuilder/windowbuilder/blob/master/org.eclipse.wb.rcp/src/org/eclipse/wb/internal/rcp/model/layout/grid/GridLayout2.java) and [GridData2](https://github.com/eclipse-windowbuilder/windowbuilder/blob/master/org.eclipse.wb.rcp/src/org/eclipse/wb/internal/rcp/model/layout/grid/GridData2.java) are old copies of the SWT layouts, which store additional information that are relevant during design time.

We should separate the designer information from the layout algorithm to make sure that our implementation matches the actual implementation.

Commencez par org.eclipse.wb.rcp/src/org/eclipse/wb/internal/rcp/model/layout/grid/GridLayout2.java et GridData2.java, puis comparez le travail associé dans issue 963 et les classes SWT correspondantes. La modification est terminée lorsque les informations spécifiques au concepteur sont séparées de l’algorithme de layout et que l’implémentation correspond au comportement de SWT.

Rédigé par le modèle d'indexation à partir du texte de l'issue.